arm/oeqa: add no-op runtime test

Machines which don't have working network stacks in a FVP can still run
a useful testimage, because it will validate that the machine will boot
to a login prompt on the console.

However, we can't set TEST_SUITES to "" because testimage assumes that
was a mistake, so add a no-op test case for use in these situations.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm/lib/oeqa/runtime/cases/noop.py

@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: MIT
+
+from oeqa.runtime.case import OERuntimeTestCase
+
+class NoopTest(OERuntimeTestCase):
+    """
+    This is a test case which does nothing.  Useful when you want to use
+    testimage to verify that an image boots, but you don't have networking so
+    none of the existing test cases are suitable.
+    """
+    def test_no_op(self):
+        return